/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.library.util;

/**
 * Circular queue for double
 */
public class DoubleCircularQueue {

    private static int INITCAP = 64;

    private int head, tail, size, minLen;
    private double[] data;

    public DoubleCircularQueue(int capacity) {
        head = tail = size = 0;
        data = new double[capacity];
        minLen = Math.max(INITCAP, capacity);
    }

    public DoubleCircularQueue() {
        this(INITCAP);
    }

    /**
     * push value into the back of queue
     *
     * @param value value to push
     */
    public void push(double value) {
        if (isFull()) {
            resize(data.length * 2);
        }
        data[tail] = value;
        tail = (tail + 1) % data.length;
        size++;
    }

    /**
     * pop value from the front of queue
     *
     * @return value in the front
     */
    public double pop() {
        if (isEmpty()) {
            throw new IllegalArgumentException("Error: Queue is Empty!");
        }
        double ret = data[head];
        head = (head + 1) % data.length;
        size--;
        if (size < data.length / 4 && data.length / 2 >= minLen) {
            resize(data.length / 2);
        }
        return ret;
    }

    /**
     * get the value in the front
     *
     * @return value in the front
     */
    public double getHead() {
        if (isEmpty()) {
            throw new IllegalArgumentException("Error: Queue is Empty!");
        }
        double ret = data[head];
        return ret;
    }

    /**
     * judge if circular queue is empty
     *
     * @return if empty, return true; else return false
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * judge if circular queue is full
     *
     * @return if full, return true; else return false
     */
    public boolean isFull() {
        return size == data.length;
    }

    /**
     * change size of queue
     *
     * @param newLength new length of queue
     */
    private void resize(int newLength) {
        double[] newData = new double[newLength];
        for (int i = 0; i < size; i++) {
            newData[i] = data[(head + i) % data.length];
        }
        data = newData;
        head = 0;
        tail = size;
    }

    /**
     * get value of given index
     *
     * @param index index
     * @return value to queue
     */
    public double get(int index) {
        if (index < 0 || index >= size) {
            throw new IndexOutOfBoundsException();
        }
        return data[(head + index) % data.length];
    }

    /**
     * get number of values in queue
     *
     * @return number of values
     */
    public int getSize() {
        return size;
    }
}
